Pneumatic actuators

ABSTRACT

A pneumatic actuator in which a double acting assembly of interconnected pistons are disposed in a common cylindrical chamber and form a series of individually expansible chambers with independent respective strokes. The pistons provide for an end connector a plurality of possible discrete positions differently spaced from a datum. A rack is mounted for lengthwise movement with said end connector, and a plunger is arranged to cooperate with the rack to secure it and the end connector in at least some of the said positions.

United States Patent [191 Wills et al.

[ Aug. 12, 1975 PNEUMATIC ACTUATORS [76] Inventors: Peter Wills, 32 Beacon Hill,

Lingfield; Zygmunt Pudlo, l 17 Three Bridges Rd., Crawley, both of England [22] Filed: Aug. 30, 1973 [21] App]. No.: 392,997

[30] Foreign Application Priority Data Sept. 7, 1972 United Kingdom 41618/72 [52] US. Cl 91/1; 91/44; 91/167 R; 4 250/231 R [51] Int. Cl. FOlb 25/26; FOlb 31/12 [58] Field of Search 91/167, 1, 44, 45, 361, 91/363; 92/5; 250/231 R [56] References Cited UNITED STATES PATENTS 2,543,522 2/1951 Cohen 250/23] R 2,931,340 4/1960 White 91/167 2,932,282 4/1960 McKinley et al. 91/45 2,969,042 l/l961 Litz et a1 91/167 3,162,365 12/1964 Gizeski 91/167 3,220,250 1 H1965 Strandquist et al. 250/23] R 3,452,645 7/1969 Barltrop 9l/l 3,510,759 5/1970 Nador 250/231 R FOREIGN PATENTS OR APPLICATIONS 1,576,079 6/1969 Germany 9l/l67 Primary ExaminerMartin P. Schwadron Assistant Examiner-Abraham Hershkovitz 5 7 ABSTRACT A pneumatic actuator in which a double acting assembly of interconnected pistons are disposed in a common cylindrical chamber and form a series of individually expansible chambers with independent respective strokes. The pistons provide for an end connector a plurality of possible discrete positions differently spaced from a datum. A rack is mounted for lengthwise movement with said end connector, and a plunger is arranged to cooperate with the rack to secure it and the end connector in at least some of the said positions.

2 Claims, 7 Drawing Figures PATENTED AUG] 2 I975 SHEET PATENTEU mi 21975 SHEET mm mm, am. 1 N m m M J 1 QM: w a PA- M um w mTN w m 4 .7 L 5 M 2.. wi U Q Q 2 A m D R QQ b P Q aw mm S N H mm Q PATENTED AUG 1 2 I975 SHEET ABCDE PNEUMATIC ACTUATORS This invention relates to pneumatic actuators adapted to move a member to any of a plurality of linearly spaced apart positions.

An actuator as described herein is particularly although not exclusively intended for use in moving matrix cases in composing machines so as to move a selected master character in the matrix to a particular operating position. In particular, two actuators, working in orthogonal directions, can be used to provide orthogonal movements of a matrix case. A pneumatic actuator according to the present invention is also suit able for use in a system as described in our prior US. Pat. No. 1 178833 wherein a plurality of charactermatrices are movable independently and wherein a character in one matrix can be moved into a respective operating position while a selected character in another matrix is in its respective operating position for producing an image of character.'

According to the present invention, a pneumatic actuator comprises a double acting assembly of interconnected first pistons forming in a common chamber a series of individually expansible chambers with independent, respective strokes and arranged to provide for an end connector a plurality of possible discrete positions differently spaced from a datum, a rack mounted for lengthwise movement with said end connector and a plunger arranged to co-operate with the rack to secure the rack and end connector in at least some of the said positions.

A counter may be disposed to co-operate with the teeth to provide an indication of the actual position of the rack and end connector with respect to the datum, means being provided to compare the indication of the actual position with an indication of a desired position to stop the rack and end connector in the desired position.

The counter may include a light source, and a photocell disposed so that its illumination by the light source is interrupted by the passage of the teeth of the rack.

As indicated hereinbefore, the invention is applicable to a print composing machine comprising a matrix of characters movable in at least one direction to select a character in the matrix for use and a pneumatic actuator coupled to the matrix for effecting said movement. The matrix may be movable in two orthogonal directions, a pneumatic actuator as described herein being provided for each direction of movement.

Reference will now be made to the accompanying drawings in which:

FIG. 1 is a plan view of a pneumatic actuator according to the invention;

FIG. 2 is a cross-sectional elevation of the actuator of FIG. 1;

FIG. 3 is a part sectional view of one of the pistons of the actuator shown in FIGS. 1 and 2;

FIG. 4 is a sectional view of a control valve of the pneumatic actuator shown in FIG. 2;

FIGS. 5a a and b are schematic diagrams illustrating the arrangement of parts of a counter of the pneumatic actuator of FIG. 1; and

FIG. 6 is a schematic diagram illustrating how two actuators according to the invention may be used to position a matrix case in a photocomposing machine.

The preferred form of pneumatic actuator, as illustrated in the drawings, comprises a cylinder 1 having an axial cylindrical chamber 2, in which a plurality of pistons 3 are disposed end to end. The pistons are arranged to interlock, one with its adjacent piston, so that each piston except the first has a respective stroke with respect to the preceding piston, the first piston 3a having a stroke with respect to a datum provided by an end stop 4 at the lefthand end of chamber 2. In the illustrated example, five pistons are provided in the chamber, each comprising a hollow cylindrical part 5 (see FIG. 3) which is open at one end, and a cylindrical plunger portion 6 formed integrally with the hollow cylindrical part 5 and extending axially from the nonopen end thereof. A seating ring 7 is located by a pair of circular flanges 7a on the outer surface of the hollow cylindrical part, and provides an air tight seal with the wall of the chamber 2. The plunger portion 6 of each piston except the last is slidably received within the hollow cylindrical portion of the next piston. The stroke of a given piston, with respect to its preceding piston is determined by the length of an axially extending slot 8 in the plunger portion of the said preceding piston, with which a guide pin 9 co-operates, the guide pin extending diametrically across the cylindrical portion of that given piston, and passing through the slot 8 in the plunger portion of the preceding piston. The ends of the pin 9 are fixed in the wall of the cylindrical portion.

The stroke of the first piston 3a is determined by the length of a slot 8a in a plunger portion 6a which extends into the left hand end of the chamber 3 from the end stop 4.

The strokes of the pistons may be arranged according to a binary power series.

Spaced apart along the length of the cylinder are valves 10 which are selectively operable to admit air for actuating the pistons from a pressurised air supply to the chamber 2 at the inlet ports (not shown) each so positioned in the chamber wall that regardless of the piston positions, it is never crossed by the sealing ring of the piston which it supplies or by that of the preceding piston.

The piston with the longest stroke 3b that is the one furthest to the right as shown in FIG. 2 has a hollow cylindrical portion with a guide pin, but its plunger portion is also hollow and passes through a cylindrical bore of an end cap 11. A constant air supply to the space to the right of the piston ring of piston 3b ensures that when anyone or more of the valves 10 is off, the pistons concerned are returned to their fully retracted positions, and excess air in the chamber is exhausted through the valves concerned.

The piston 3b is linked by a spring connecting mechanism 12 to a cross-bar 13 constituting an end connector. An oil filled dashpot 14 operates through a lever 15 and a connecting rod 16 attached to the lever at a pivot 15a on the cross-bar to damp down the movement of the actuator at highspeed whilst not impeding movement of the pistons at slower speeds. The dashpot and lever have been omitted from FIG. 2 for the sake of clarity.

Attached to the cross-bar 13 is a rack 17 which is moveable by the piston movement in lengthwise manner. The rack 17 carries teeth 18 which are spaced apart according to the spacings of the individual positions that can be provided by appropriate selective operation of the valves 10. A rack engaging mechanism 19 through which the rack passes, is provided. This mechanism comprises a locating plunger 20 attached to a piston 21 which is slidable in a cylinder 22. The piston is moveable against the bias of a spring 23 by air admitted to the lower part of the cylinder 22 by a valve 24.

Details of the construction of the valves 10 and 24 are given in FIG. 4. A valve block 25 is attached to the side of the cylinder Land has a plurality of outlet passages 26 each of which connects with one of the inlet ports to the chamber 2. A longitudinal bore 27 in the valve block carries the air supply, and individual supply bores 28 pass the air to a ball valve 29 which is operable by energisation of a solenoid 30, consequent movement of pivot arm 31 against bias of a return spring 32 and the resulting removal of closure pressure on a valve rod 33, to admit air to the outlet passage 26. Deenergisation of the solenoid causes the spring 32 to pivot the pivot arm 31 so as to bear on the valve rod 33; this seats the ball-valve 29 so as to interrupt the air supply, and permit air from the cylinder to pass out through exhaust passage 34.

As can be seen from FIG. 1, the main air supply path, indicated by broken lines passes from the valve block and ends at valve 24 after passing through space 35 in the cylinder 1 to the right of the piston 3b as viewed in FIG. 2. t

A counter 36 is provided adjacent themechanisrn 19 for counting the teeth of the rack as they move past. As shown in FIGS. a and b the counter includes a pair of light sources 37 .on one side of the rack and apair ,of photocells 38 on the other side, each photocell being positioned so that it will receive light from its respective source and so that the light pathbetween it andits source will be interrupted intermittently by movement of the teeth of the rack. The light sources and corresponding photoelectric cells are so positioned that the light beam between one pair is interrupted by the teeth of the rack momentarily before that of the other pair, according to the direction of movement of the rack. This enables a computer which controls the operation of the actuator to determine the direction and extent of movement of the rack, and therefore its position at any time. y

The actuator is shown in FIG. 2 with all the pistons 3 in their 'fully retracted positions, that is all the valves are off. Signals from a control computer are supplied to the valves 10, and the solenoids of certain valves, selected according to the required displacement of the rack, are energised. Valve 24 is also switched on so that air is admitted to cylinder 22, beneath piston 21 causing that piston to move upwardly, and the locating plunger 20 to disengage from the rack. The selected pistons then assume their fully extended positions, and the rack and cross bar are displaced by the required matrix case would be moveable in at least one direction in order to bring any one of a plurality of master characters into an operating position. Once the matrix case has been positioned for one character and is held by the engagement of locating plunger 20 and rack, the valves 10 may be set to position the matrix case for the following character. This will almost certainly cause some of the pistons to move, and the spring connecting mechanism l2 acts as a shock absorber and prevents the transmission of shock to the rack. When next the plunger 20 lifts, the pistons take up their new positions.

The positions that can be provided by selective operation of the pistons and the co-operating rack and plunger are matched to the spacing of the characters in the row of the matrix the matrix may also be moveable at right angles by another actuator as described above in order to provide two dimensional selection in an array of characters.

The cylinder may be lubricated by mixing oil with the air supply.

The constant air pressure in the space will easily be overcome by the pressure acting on a layer area for movement of the pistons to the right, but will always return any pistons whose valves are set to exhaust, to their retracted positions.

We claim:

1. Ina pneumatic actuator having a double acting assembly of interconnected first pistons forming in a common chamber, a seriesof individually expansible chambers with independent, respective strokes and arranged to provide for an end connector a plurality of possible discrete positions differently spaced from a daturn, a rack mounted for lengthwise movement with amount towards the right. The counter counts the teeth as they move past, and the number counted is compared by the computer with a number representing the said end connector, said rack being provided with a plurality of teeth with recesses between said teeth, a plunger arranged to cooperate with the rack to secure the rack and end connector in at least some of the said positions, one end of the plunger being shaped for engagement with said recesses, a second piston for moving said plunger relative to the rack, to engage and disengage from the rack, and a plurality of valves for connecting selected ones of said chambers to an air supply,

wherein the improvement comprises counter means including a first light source and a first photocell disposed adjacent said rack so that on opposite sides of the path of said teeth the illumination by the light source is interrupted by the passage of the teeth of the rack, thereby to cause said photocell to produce, when said rack is moved,.an output having a number of successive interruptions, the number of interruptions providing an indication of the extent of movement of the rack.

2. A pneumatic actuator according to claim 1, wherein said counter means further includes a second light source and a second photo electric cell, being disposed adjacent said rack and in spaced-apart relation ship from said first light source and photocell respectively, such that the interruptions of the illumination of one of said cells and consequently also of its output, occurs momentarily before that of the other cell, and the order in which the interruptions in the outputs occur provides an indication of the direction of movement of the rack. 

1. In a pneumatic actuator having a double acting assembly of interconnected first pistons forming in a common chamber, a series of individually expansible chambers with independent, respective strokes and arranged to provide for an end connector a plurality of possible discrete positions differently spaced from a datum, a rack mounted for lengthwise movement with said end connector, said rack being provided with a plurality of teeth with recesses between said teeth, a plunger arranged to cooperate with the rack to secure the rack and end connector in at least some of the said positions, one end of the plunger being shaped for engagement with said recesses, a second piston for moving said plunger relative to the rack, to engage and disengage from the rack, and a plurality of valves for connecting selected ones of said chambers to an air supply, wherein the improvement comprises counter means including a first light source and a first photocell disposed adjacent said rack so that on opposite sides of the path of said teeth the illumination by the light source is interrupted by the passage of the teeth of the rack, thereby to cause said photocell to produce, when said rack is moved, an output having a number of successive interruptions, the number of interruptions providing an indication of the extent of movement of the rack.
 2. A pneumatic actuator according to claim 1, wherein said counter means further includes a second light source and a second photo electric cell, being disposed adjacent said rack and in spaced-apart relationship from said first light source and photocell respectively, such that the interruptions of the illumination of one of said cells and consequently also of its output, occurs momentarily before that of the other cell, and the order in which the interruptions in the outputs occur provides an indication of the direction of movement of the rack. 